The recent use of thrombolytic drugs to effectively treat ischemic stroke marks a milestone in the campaign against this common neurological disease. Although a significant advancement, this treatment is not suitable for all patients, such as those who are experiencing a hemorrhagic stroke or those receiving treatment more than three hours after stroke onset. Hospital staff can use computed tomography (CT) scans to easily rule out hemorrhages. More difficult, however, is estimating the therapeutic window of time. Late treatment still brings the hemorrhagic risk of thrombolytic treatment, but it faces an increasingly uncertain state of the neural tissue. A rapid, inexpensive, and noninvasive cerebral monitoring technique could help hospital staff to determine neural-tissue state as well as to assess the effectiveness of thrombolytic treatment. In this Phase I project, we will use dense-array electroencephalography (EEG) to collect near-continuous, stroke-related EEG so that we can evaluate the ongoing pathophysiological evolution of the ischemic tissue. Spectral and coherence analyses of the raw EEG data will enable us to characterize EEG changes in these records. The results from this work will go toward the development of a rapid, inexpensive, noninvasive, accurate stroke-monitoring device based on dense-array EEG. PROPOSED COMMERCIAL APPLICATIONS: EEG is highly sensitive to stroke-related pathophysiology. Its use in surgical monitoring is well known; however, its potential as a practical, inexpensive stroke-monitoring technology heretofore has been overlooked. If we can demonstrate that stroke-related EEG changes can help inform treatment decisions, every hospital and clinic treating acute stroke would require this monitoring system -an obviously lucrative prospect, with a worldwide market potential approaching $1 billion.